A number of techniques have been proposed or suggested for determining whether or not a person is “present” at a given device, location or application. Presence information is becoming increasingly important for many applications. For example, as friends and colleagues become more distributed in time or location (or both), it becomes even more desirable for a user to determine, prior to a given communication attempt, whether or not the intended recipient of the contemplated communication is currently available at one or more communication devices. The provided presence information allows a user to make a more informed decision about how to best communicate with another person. In this manner, productivity is enhanced by enabling a better selection of the best way to contact the other person. This informed choice leads to a more efficient, productive and cost effective communication.
Determining a user's presence and availability at a given device, location or application can generally not be done with certainty. Presence and availability are a prediction of current presence and availability based on presence and availability in the past (i.e., either the immediate past or over an extended history). For example, presence information based on login activity (e.g., whether the user is currently logged on to a given service) can grow stale over time, since a user may remain logged in to an application for several days at a time. Thus, many presence-tracking systems supplement the user login activity with other determinable user activity, such as keyboard or mouse activity and whether a user remains idle for a time period exceeding a specified interval. Existing presence awareness systems can distinguish between a user who is connected to the service (present) or not connected to the service (absent), and most systems allow some sort of busy or unavailable flag to be set.
A number of techniques have been proposed or suggested for evaluating the likelihood that a user will be present at a device or location at some time, t, based on knowledge that the user was present at the device or location at some prior time. Such techniques are sometimes referred to as “presence aging.” For example, Horvitz et al., “Coordinate: Probabilistic Forecasting of Presence and Availability,” 18th Conf. on Uncertainty and Artificial Intelligence, 224-233 (July, 2002), describes a system that attempts to predict a user's presence and availability based on historical data, as well as future known data about the user's activities, for example, from a user's calendar. The Horvitz system attempts to evaluate the probability of the user's presence and availability being associated with one or more discrete presence/availability states.
While existing presence awareness systems provide valuable presence information, they suffer from a number of limitations, which if overcome, could further improve the ability of users to efficiently communicate. For example, existing presence awareness systems are typically proprietary, closed architecture systems that only provide presence information within the domain of the service provider (i.e., one service subscriber can only determine if another service subscriber is present). Moreover, such systems typically require the user to actively perform a system login before these systems can track user presence and availability. In addition, existing presence aging techniques employ discrete stepwise functions that consider a presence state, such as “available,” to be in full effect until a certain time interval (or event) has passed, then the presence state changes to another, generally lower, discrete value, such as “away.”
A need therefore exists for methods and systems that can evaluate a number of different sources of presence information for a user, independent of the providers of the devices and systems that constitute presence sources and without requiring active user logins, using a presence agent associated with each source of presence information. A further need exists for a method and apparatus for evaluating presence information on a continuous scale.